package 机试题16年;

import java.util.Scanner;

/**
 * Created by hest0 on 2017/4/18.
 */
public class 搬圆桌 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int r = sc.nextInt();
            int x = sc.nextInt();
            int y = sc.nextInt();
            int x1 = sc.nextInt();
            int y1 = sc.nextInt();
            double res = Math.sqrt(Math.pow(y1 - y, 2) + Math.pow(x1 - x, 2));
            System.out.println((int) res / (2 * r));
        }
        sc.close();
    }
}
